Non-melanosomal regulatory factors in melanogenesis

The enzyme activity of tyrosinase, catalase, and peroxidase and the number of metal ions in melanogenic subcellular compartments in pigment cells were measured. Coated vesicles were richest in tyrosinase and catalase, whereas premelanosomes had the highest amount of peroxidase. Among metals ions examined, copper, zinc, and iron were more concentrated in pre-melanosomes than in coated vesicles. A quantitative analysis revealed that peroxidase served to enhance eumelanin polymer formation from monomers in the presence of hydrogen peroxide and metal ions, especially copper ions, which had the greatest enhancing effect on the conversion of monomers to polymers.